A critical review on metal-based catalysts used in the pyrolysis of lignocellulosic biomass materials

• Published in: Journal of environmental management Vol. 299; p. 113597
• Main Authors: Tawalbeh, Muhammad, Al-Othman, Amani, Salamah, Tareq, Alkasrawi, Malek, Martis, Remston, El-Rub, Ziad Abu
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2021
• Subjects: Bio-oil; Biomass; Lignite; Lignocellulosic materials; Metal-based catalysts; Pyrolysis; Pyrolysis; Metal-based catalysts; Lignite; Biomass; Lignocellulosic materials; Bio-oil
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2021.113597

This review discusses the technical aspects of improving the efficiency of the pyrolysis of lignocellulosic materials to increase the yield of the main products, which are bio-oil, biochar, and syngas. The latest aspects of catalyst development in the biomass pyrolysis process are presented focusing on the various catalyst structures, the physical and chemical performance of the catalysts, and the mode of the catalytic reaction. In bio-oil upgrading, atmospheric catalytic cracking is shown to be more economical than catalytic hydrotreating. Catalysts help in the upgrading process by facilitating several reaction pathways such as polymerization, aromatization, and alkyl condensation. However, the grade of bio-oil must be similar to that of diesel fuel. Hence, the properties of the pyrolysis liquid such as viscosity, kinematic viscosity, density, and boiling point are important and have been highlighted. Switching between types of catalysts has a significant influence on the final product yields and exhibits different levels of durability. Various catalysts have been shown to enhance gas yield at the expense of the yields of bio-oil and biochar that shift the overall purpose of pyrolysis. Therefore, the catalytic activity as a function of temperature, pressure, and catalyst biomass ratio is discussed in detail. These operational parameters are crucial because they determine the overall yield as well as the ratio of the oil, char, and gas products. Although significant progress has been made in catalytic pyrolysis, the economic feasibility of the process and the catalyst cost remain the major obstacles. This review concludes that the catalytic process would be feasible when the fuel selling price is reduced to less than US $ 4 per gallon of gasoline-equivalent, and when the selectivity of catalysts is further enhanced. •The technical aspects for improving the efficiency of the pyrolysis process are discussed.•The latest catalyst development introduced significant changes in the pyrolysis process.•The operational parameters are the key factors responsible for increasing the product yield.•The economic feasibility of the process and the catalyst cost remain the major obstacles.